Hydraulic pump



Sept. 9, 1958 E. A. ARP 2,850,981

HYDRAULC PUMP Filed March 8,. 1956 4 Sheets-Sheet 1 F1511 FIEE` E Sept.9, 1958 E. A. ARP 2,850,981

HYDRAULIC PUMP 4 Sheets-Sheet 2 Filed March 8, 1956 CZ'E. E

`I\-\\I\ \4\ INVENTOR. 26 67 26 E14/44D ,4. RP

A Tram/srs Sept. 9, 1958 E. A. ARP 2,850,981

' HYDRAULIC PUMP Filed March 8, 1956 4 Sheets-Sheet 3 EF1-ZTL?. 4 46INVENTOR. Zuma 4 ARP rroRA/Eys Sept. 9, 1958 E. A. ARP l 2,850,981

HYDRAULIC PUMP Filed March 8, 1956 4 Sheets-Sheet 4 IN VEN TOR. .EA/up,4. ARP

Irren/vers United States Patent HYDRAULIC PUMP Ewaid A. Arp,Minneapolis, Minn., assignor to "Echin- Arp Manufacturing Company,Minneapolis, Mann., a corporation of Minnesota Application March, 1956,Serial No. 576,353

s anims. (ci. rc3/m49) ycylinder of lan hydraulic press.

In a device made according to the present invention, a pair of airdriven pistons are connected integrallypto each other each inoperational relationship to one of a pair of air cylinders in such a waythat air pressurel exerted in either of the cylinders will tend to forcethe opposite piston toward the head .end of its cylinder. Each of theseair driven pistons has an oil displacement plunger integrally attachedthereto and mountedto extend inside of one of a pair of oil displacementchambers. Movement of each air driven piston away from the head end ofits air cylinder causes the displacement plunger associated therewith tomove farther into its displacement chamber. Movement of eachdisplacement plunger into its displacement chamber causes a valveopening to a source of hydraulic iluid to be closedY and a valve openingto the main cylinder to be open. Oil in said chamber will be forcedthrough said open valve into said cylinder. Switching means responsiveto the positioning of each of said air driven pistons with respectv tosaid air cylinders causes each of said air cylinders to become closedtoa source of air under pressure and opened to exhaust when said airdriven piston reaches a position adjacent the head end of said aircylinder and to become closed to exhaust and opened to air underpressure when said air driven piston reaches a position spaced fromthehead end of said cylinder. Such a hydraulic pump will lind.usefulness wherever it is desirable to obtain a high ratio between thehydraulic working pressure and the driving air pressure and where, forexample, at the same time, the length of the travel of the air drivenpiston is short with respect to' the length of travel of thehydraulically drivenl ram. The press shown and described herein willrbeparticularly useful in forcing wrist pins into place in connecting rodshaving no wrist pin bushingsl therein to pivotally mount automotivecylinders on said connecting rods;7 and to remove said wrist pins fromsaid rods to free said cylinders therefrom.

In the drawings,

Fig. 1 is a front elevational viewof a hydraulic press made according tothe present invention;

Fig. 2 is a side elevational view of the hydraulic press ot Fig. 1;

Fig. 3 is an enlarged sectional view taken substantially on the line 3 3in Fig. 2;

Fig. 4 isan enlarged horizontal sectional view taken.

on theline 4 4 in Fig: l;

Fig. 5 is an enlarged fragmentary view of a portion ofthe hydraulic.press as seen inthe lowerright hand corner of Fig. 4; f

Fig. 6 is an enlarged sectional view taken on theline 6`-6in Fig. 3;

, 2,850,981 Patented Sept. 9, 1-958 ice ber 11, a main drive cylinder 12supported on said base',A

a pair of upright support columns 13, 13, ,a lheard 14 supported on saidcolumns, and an adjustable head rod 15 mounted in said head andextending downwardly therefrom. A ram assembly 16 includes a rarn table17 integrally connected to a main driven piston 18 which is operablysituated in the main drive cylinder 12; Introduction yof hydraulic uidunder pressure into the main drive cylinder 12 between the bottom endthereof and the main piston 18 will tend to cause the main piston torise in the cylinder to force the ram table 17 in direction towards theadjustable head (rod 1S. The head 14 can be supported on the uprightsupport column 13, 13 at any convenient height depending upon the sizeof the article uponwhich the press is to operate. For this pur'- pose aplurality of horizontal openings 19 are provided in each of the supportcolumns 13 and corresponding horizontal openings 20 are provided in thehead 14. A pair of support pins 21, 21 are adapted to extend throughopenings 20 and into openings 19 to position the head at any desiredvertical location. The adjustable head rod 15 is threadably mounted inthe head 1,4,so that the vertical position of the head rod can bereadily adjusted with respect to the location of the ram table 17.

A pair of oppositely disposed airV cylinders 22 and-23 form a part ofsaid base' member 11. An air driven piston Z4 is operably mounted insaid air cylinder 22'and an air driven piston 25 is operably mounted insaid air cylinder 23. Said air driven pistons are connected to eachother by means of air driven piston connecting rods 26 which extend outof the open ends of the cylindersr 22 and 23 land through the basemember 11. A pair of' oil displacement chambers 274 and 28 are providedwithinthe base member 11 and oil displacement plungers 29 and 30 areintegral with air driven pistons 24 and 25l respectively, and are inposition to exetnd inside of said oil displacement chambers 27 and 28respectively. Y

The upright support columns 13, 13 are each mounted on the base member11 as at 31 and an oil sump tank 32 extends downwardly from said supportcolumn to completelyY enclosesaid base' member 11.v -Oil filter neck33on top of said tank 32 is provided with an oilcap 34 which can beremoved from the `filter neck to allow introduction of replacement oilinto the tank. Thetop levelof the oil in saidy tank 32 isv indicated atV3S in Fig.V 3.

Air control cylinders 36 and 37 are integralfwith the base member 11.Air control piston 38 -is operably mounted in air control cylinder 36'and air control piston 39 is operably mounted in air control cylinder3,7. Control pipe 40 extends from the head end of air control cylinder36`^to an air control ring 42 which is situated.

openings 44'in`th'e air cylinder 22 open from the'int'eriorV oflsaidcylinderV into the control ring 42. A' pluralityl of Vop`enings"45 intheair cylinder 23 open from thel interiori of said air cylinder into thecontrol 1'ir1`g43'. Said openings 44 are Aso,V positioned that: thehead'end ofthe? air cylinderi22 will be" open to said air control ring42l through said openings when the air driven piston 24 is positionedy'so that oildisplacement plunger 29 iscausing maximum displacement ofoil in oil displacement chamber 27. When the air driven piston 24 is inany other position, it serves to seal off connection between said headend of said air cylinder 22 and the interior of the air control ring 42.Said openings are so positioned that the head end of4 air cylinder 23will be open to said air control ring 43 when air driven piston 25 ispositioned so that oil displacement plunger 30 is causing maximumdisplacement of oil in the oil displacement chamber 28. When the airdriven piston 25 is in any other position, it serves to seal offconnection between the head end of said air cylinder 23 and the interiorof said air control ring 43.

High pressure air enters the oil sump tank 32 through the air supplypipe 46 from a compressor or other source (not shown). Air supply pipe46 opens to a main air valve 47 which is mounted on the front wall ofthe oil sump tank 32 as best seen in Figs. 4 and 5. Details of theinternal construction of this main air valve 47 are best seen in Fig. 5and will Vbe set out in detail later in the specification. The valve isoperated by depressing a main air valve control lever 48. This permitsthe high pressure air in pipe 46 to pass into an air pipe 49 which leadsoutwardly from the main air valve 47. The air pipe 49 is bifurcated andis connected to the base member 11 at a position between the aircylinder 22 and the air control cylinder 36 on one end of said castingand to a position between air cylinder 23 and air control cylinder 37 onthe other end thereof. A high pressure air supply passageway 50 is openthrough base member 11 from inside of the head end of the air cylinder'22 to one end of the air pipe 49 and a high pressure air supplypassageway 51 is open through said base member 11 from inside of thehead end of the air cylinder 23 to another end of the air pipe 49. Anexhaust passageway 52 extends from inside said head end of said aircylinder 22 to outside of the base member 11 and an exhaust passageway53 extends from inside of the head end of air cylinder 23 to a positionoutside of said base member 11. A slideable, stem type valve 54 isintegrally connected to air control piston 38 and air control piston 39.It extends through the base members 11 in such a manner as to intersecthigh pressure air supply passageways 50 and 51 and exhaust passageways52 and S3. Said slideable valve 54 is provided with four portsdesignated 55, 56, 57 and 58. When air control piston 39 is at itsmaximum position away from the head end of air control cylinder 37, port55 is alined with high pressure air supply passageway 50 to allowpassage of air therealong and port S7 is in alinement with exhaustpassageway 53 to allow passage of air along said passageway. Passageways51 and 52 will be blocked by said valve at this time. When air controlpiston 38 is at its maximum position away from the head end of the aircontrol cylinder 36, passageways 50 and 53l will be blocked but port 56will be alined way 52 to provide for air way and port 58 supplypassageway passageway.

The oil displacement chambers Y27 and 28 are generally cylindrical andextend horizontally through the center of the base casting 11 and areconcentric with the air driven pistons 24 and 25 and the oildisplacement passage through saidV passagewill be alined with highpressure air 51 to allow passage of air along this plungers 29 and 30.These chambers 27 and 28 are` separated from each other by a plug 59which has a cylindrical passageway-60 extending therethrough. An oilintake valve member 61 extends through the passageway 60 in the plug 59and includes a' disc valve 62 positioned to be capable of restingagainst an outer face of the plug 59 to close ofI the passageway `60fromthe oil displacement chamber 27 and a disc valve63 capable ofresting against an outer face of the plug 59 to close off the passageway60 from 28. The disc valves 62 and 63 are permanently positioned withrespect to each other by means of a disc with exhaust passagei the oildisplacement chamber 4 valve connecting rod 64 which is constituted as alength of pinion stock having a plurality of outwardly extending teethresting in contact with the cylindrical inner surface of the opening 60.These teeth are cut away as at 66 so that oil passing through theopening 60 can llow between each of said teeth.

An oil supply intake opening 67 extends from the bottom surface of thebase member 11 up into the cylindrical passageway 60. An oildisplacement chamber discharge conduit 68 extends from the oildisplacement chamber 27 into the main drive cylinder 12 and an oildisplacement chamber discharge conduit 69 extends from the oildisplacement chamber 28 into said drive cylinder 12. A reed valve 70includes an end portion 71 which is positioned to normally close theopening between the discharge conduit 68 and the main drive cylinder 12and an end portion 72 which is situated to normally close the openingbetween the discharge conduit 69 and said cylinder.

As best seen in Figs. 7 and 8, a regulator valve 73 for preventing thebuild up of destructive pressure inside of the main drive cylinder 12and for manually relieving the pressure therein to allow the main piston18 and the ram table 17 to move away from head rod 15 is mounted on saidmain drive cylinder at position adjacent the closed bottom end thereof.The regulator valve casing 74 is provided with an oil pipe 75 whichopens from the interior of the main drive cylinder 12 to the interior ofsaid casing 74. A plurality of release passageways 76 extend through thecasing 74 to intersect said oil pipe 75. A ball valve 77 is pressed bythe piston 78 under the action of spring 79 to have normal sealingrelationship to a valve seat 80 to seal oil pipe 75 from said reliefpassageways 76. Piston rod 81 extends outwardly of the valve casing 73and is pivotally connected in an eccentric manner to a regulator valvecontrol rod 82 as best seen in Fig. 7. A regulator valve cover 83 isthreadably situated on the regulator valve casing 74 and provides a flatend surface 84 adjacent to or against which the regulator valve controlrod can rest. `This control rod 82 extends outwardly through the sidewall of the oil sump tank 32 as best seen in Fig. 4 and the regulatorvalve control rod handle 85 is attached to it outside of the tank.

Referring now particularly to Fig. 5, the main air valve 47 includes amain air valve casting 86, a conical main air valve member 87 normallyheld in sealing relationship to close the opening of the air pipe 49 tothe interior of said valve casting. The spring 88 serves to urge saidconical valve member toward this closed position and a valve stem 89extends outwardly through said casting 86 to be fastened in pivotalrelationship to an eccentrically placed inner end of a main air controllever rod 90. The other end of said rod 90 is mounted in an outer wallof the oil sump tank 32 to be concentric with said mounting. Main aircontrol lever 48 is integrally attached to said concentric end of saidcontrol rod 90.

Operation When it is desired to use the hydraulic press, the work to beacted upon by the press is placed on the ram table 17 which will, ofcourse, be in its lowest position. The head 14 will be supported on theupright support column 13, 13 as close as practicable to the work on theram table and the adjustable head rod 15 will be rotated to lower'it toposition immediately adjacent or in contact with the work.

To cause the ram table 17 to move in direction toward the head rod 15,the main air valve control lever 48 is depressed by applying a downwardforce on a chain 91 which is attached to an outer end thereof. This maybe done by the foot of the operator so as to leave both hands free tokeep the work properly alined with the head rod 15 as the ram tablerises. Downward movement of 'the main air control lever 48 will causethe main air control lever rod 96 to rotate to moveV the, valvestern 89and the conical valve member S7 in direction away from air pipe 49against the action of spring 88. This allows the air under pressure inthe air supply pipe 46 to pass into air pipe 49 which carries the airinto the high pressure air supply passageway 5l) and the high pressureair supply passageway 51. In the event that the parts are initiallypositioned as disclosed in Fig. 6, port 55 in the slideable stem typevalve 54 is in alinement with air sup` ply passageway 5d and the airfrom the air supply pipe 46 and air pipe 49 will pass along the lengthof this pas sageway 5@ and into air cylinder 22. This air under pressurewill cause the air driven piston 24 to be moved in direction to theright as seen in Fig. 6 to cause oil displacement plunger 2% to enterthe oil displacement chamber 27. Build up of pressure in the oildisplacement chamber 27 due to the entry of displacement plunger 29 willcause oil intake valve member 61 to move to the right as seen in Fig. 6to close the vertical passageway 60 with respect to displacement chamber27. This build up of pressure in chamber 27 will also cause the contentsof that chamber to be forced up into oil displacement chamber dischargeconduit 68 and to lift the end portion 7i of the valve 70 from theopening of said discharge conduit 68 to allow the contents of said icause the main piston 18 to move upward to carry the ram table 17 closerto head rod 15.

Since the air driven piston 24 is connected to; the air v driven piston25 through the instrumentality ofV air driven piston connecting rods 26,movement of piston 24 to the right as seen in Fig. 6 will cause asimilar movement of piston 25 to the right as seen in thatfigure. When,port 55 in the slideable stem type vvalve 54 is in alinement with theair supply passageway 50, the port 57` in said valve 54 is in alinementwith the exhaust passageway 53. This means that when the air drivenpiston 25'moves to the right, the air in the air cylinder 23 is free tomove through exhaust passageway 53, and port 57` to the atmosphere. Asthe air driven piston 25 moves to the right, the oil displacementplunger is also moved tothe right to vacate the oil displacement chamber28. This will cause a reduction of pressure in the oil displacementchamber 23 and consequently the end portion 72 of the reed valve '76will be held firmly iny place to close the oil displacement chamberdischarge conduit 69` with respect to the main cylinder 12 because ofthe actionof the oil under pressure in that cylinder 12. Since thedisc,v

valve 62 is held in position against an o uter surface of the plug 59,the disc valve 53 will be held in position spaced from an oppositeVouter surface of said plug 59 through the instrumentality of the discvalve connecting rod 64. Since the oil level in the sump tank 32 is wellabove the opening of the oil supply intake conduit 67 into said tank,reduction of pressure in the oil displacement chamber 25 caused bymovement of the oil displacement plunger 30 out of the chamber willinduce a llow of oil from said sump tank through the oil supply intakeconduit 67, into the cutvawayportion ofthe disc valve connecting rod 64,past the teeth 65 on said rod and the disc valve 63 into the chamber 28.This ow is induced by the pressure of the atmosphere on thev oil in thesump tank and the low pressure caused .by the withdrawal of plunger 30.

As the air driven piston 24 moves to the right, it willy finally reach aposition when the openings 4,4 in the ai'r cylinder 22 are between thepiston 24 and the closed end of said air cylinder. When this happens,there. willbe a flow of air under pressure throughthe openings v 44',into the air control ring 42, through the air-control pipe and into theair control cylinder 36. Introduction'of high pressure air into the aircontrolcylinder 36" will seen in Fig. 6. This movement will cause asimilar movement to the right of slideable stem type valve 54 and aircontrol piston 39. Movement of the valve 54 will cause the port 56therein to become alined with exhaust passageway 52 and the port 58 tobecome alined with high pressure. air supply passageway 51. The port 55will move out of alinement with high pressure air supply passageway 50causing the valve 54 to block that passageway and the port 57 will moveout of alinement with exhaust passageway 53 causing said valve 54 toblock that passageway. Since at this positioning of the parts air drivenpiston 25 is to the right of the openings 4S in the air cylinder 23 asseen in Fig. 6, the air discharged from the air control cylinder 37 dueto the movement of air control piston 39 will pass along air controlpipe 41, through air control ring 43 and the openings 45 and out of theopen end of the air cylinder 23 to the atmosphere.

With the opening of air cylinder 22 to exhaust through the exhaustpassageway 52 `and port 56 in valve 54, and with the opening of aircylinder 23 to the high pressure air supply through the supplypassageway 51 and port dit, air driven piston 25 will be caused to moveto the left as seen in Fig. 6 and will carry with it, as previouslyexplained, air driven piston 24. Disc valve 63 will move against plug 59to prevent ilow of oil out of the oil displacement chamber 23 back intothe sump tank and the high pressure of the oil in said displacementchamber 28 will cause the end portion 72 of the reed valve 7h to belifted as oil from said displacement chamber 2S and the dischargeconduit 69 Hows into the main cylinder l2. This will further increasethe pressure of oil in the main cylinder and will tend to cause the mainpiston if? and consequently the ram table 17 to be moved in upwarddirection. This reciprocating action of the air cylinders, the oilintake valve member, the air control pistons and the slideable stem typevalve 54 will continue to build up.

thel pressure in main drive cylinder 12 and to force main piston 18 andram table 17 in direction toward head valve 15 until the operation beingperformed on ti c wor is accomplished or until the maximum safe Workingpres sure is obtained in the main `cylinder 12.

As will be best seen in Fig. 7, this pressure in the main cylinder 12and exerted in `oil pipe 75 tends to cause ball valve 77' to move fromthe valve seat 86 against the action of spring 79. When the maximumdesirable or sate working pressure is reached in the main cylinder andconsequently in the pipe '75, the construction and arrangement of theparts will be such that the pressure against the ball valve 77 will justovercome the force of the spring 79 and the ball valve will move out ofcontact with the, valve seat E@ to allow Ithe pressure in the maincylinder 12 to be relieved as oil flows along pipe and out throughrelief passageway '76. Oil passing out of these relief passageways 76will, of course, fall back into the sump tank 32 in which the regulatorvalve 73 is situated.

Whenever the main air valve control lever 48 is relleased to allowspring S8 to forcel conical main air valve member S7 back to position toclose the air pipe 49 from the air supply pipe 46, the reciprocatingaction of the air driven pistons, the oil intake valve member and theair control pistons will cease. The reed valve 70, however, will preventany back flow of oil into either of the oil displacement chamberdischarge conduits 65 and 69. 1n order to relieve the pressure andrelease the oil from the main cylinder 12 so that the main piston 13 canreturn to position adjacent the closed end of that cylinder to allow theram table 17 and the work thereon to move away from and out of contactwith adjustable head rod'l, regulator valve control rod handle isoperated in an upward direction as seen in Fig. 2 to cause regulatorvalve control rod 82 to be rotated kin a counter-clockwise directionasseen in Fig. 7; resting againstflat end surface of regulator valvecover i825; this rotation will cause the point of eccentric pivotalcause the air control piston 38 to move to the right as `75 connectionof piston rod to said regulator valve cun- Since this control rod 82 is.

7 trol rod 82 to move in direction away from said flat end surface 84and consequently will move the piston 78 against the action of spring 79in direction away from ball valve 77. The pressure in the main cylinderl2 and consequently in oil pipe 75 will cause the ball valve 77 to bemoved away from valve seat 80 to relieve the pressure in said maincylinder and to allow passage of oil from said cylinder out throughrelief passageways 76 and back into the sump tank 32. This relieving ofthe pressure will allow the main piston 18 and the ram table 17 to moveaway from head rod so that the work can be removed from the press.

It is to be noted that while the regulator valve 73 and the main airvalve 47 employ certain springs to accomplish seating of the valvemembers against the valve seats, the rest of the mechanism is entirelypositive in its action and does not involve the use of springs which areapt to fatigue and fail.

As a comparison of the cross sectional areas of the air cylinders 22 and23 with respect to the cross sectional areas of the oil displacementplungers 29 and 30; and of the cross sectional areas of the displacementplungcrs 29 and 30 with respect to the cross sectional area of the maincylinder l2 will indicate, a high ratio of pressure exerted by ram table17 to the pressure of the incoming air can be obtained. For example, themachine will work very well at a ratio of l0() to l.

The length of stroke of the main piston 18 is limited only by the amountof oil in the sump tank 32 and the length of the main cylinder 12. Nolimitation of length of travel is imposed by any physical limitations ofthe air and oil pumping mechanism.

What is claimed is:

l. A hydraulic pump including first and second air cylinders, first andsecond air driven pistons operably mounted in said cylinders, means foriixedly positioning each of said pistons with respect to the other, anoil displacement chamber, a discharge conduit open from saiddisplacement chamber to a location for use of hydraulic fluid underpressure, a one way valve for permitting ow of oil from saiddisplacement chamber through said discharge conduit to said location foruse, an oil supply tank, an oil intake conduit open from said supplytank to said displacement chamber, a one Way valve for permitting tiowof oil from said supply tank through said oil intake conduit to saiddisplacement chamber, an oil displacement plunger supported on one ofsaid first and `second air driven pistons to move therewith from aposition substantially entirely within said displacement chamber to aposition substantially entirely without said displacement chamber, firstand second air supply passageways for delivering air under pressure froma source thereof to said first and second air cylinders respectively,first and second exhaust passageways each extending from inside of thecorresponding air cylinder to the outside thereof, first and second aircontrol cylinders, rst and second air control pistons operably mountedin said first and second air control cylinders respectively, means forpreventing relative movement of said first and second air control pistonwith respect to each other, said air control pistons being moveable withrespect to said air control cylinders between a `first position havingsaid iirst air control piston adjacent a head end of said first aircontrol cylinder and said second air control piston spaced from a headend of said `second air control cylinder and a second position havingsaid first piston spaced from said head end of said first lair controlcylinder and said second piston `adjacent said head end of said secondair control cylinder, first and second air control passageways each openfrom the interior of the corresponding air cylinder to the interior ofthe corresponding air control cylinder, each of `said air controlpassageways being positioned to be open to said air cylinder at a sideof the air driven piston adjacent its air supply passageway when saidair driven piston is positioned adjacent a head end of said laircylinder and to be sealed off from said air supply passageway by saidair driven piston when said piston is in a position spaced from saidhead end of the airpcylinder; and valve means operative when said firstand second air control pistons are in said first position to allowpassage through said first air supply passageway and said second exhaustpassageway and to block passage through said rst exhaust passageway andsaid second air supply passageway and when said first and second aircontrol pistons are in said second position to block passage throughsaid first air supply passageway and said second exhaust passsneway andto allow passage through said first exhaust assagewsy and said secondair supply passageway.

2, A hydraulic pump including an oil displacement chamber, a dischargeconduit open from said displacment chamber to a location for use ofhydraulic fluid under pressure, a one way valve for permitting llow ofoil from said displacement chamber through said conduit to said locationfor use, an oil supply tank, an oil intake conduit open from said supplytank to said displacement chamber, a one way valve for permitting flowot oil from said supply tank through said oil intake conduit to saiddisplacement chamber, an air cylinder', an air driven piston operablymounted in said cylinder, an oil displacement plunger supported on saidair driven piston to move therewith from a position substantiallyentirely within said displacement chamber to a position substantiallyentirely Without said displacement chamber, an air supply passageway fordelivering air under pressure from a source thereof `to said aircylinder, an exhaust passageway open from inside said cylinder tooutside thereof, an air control cylinder, an air control piston operablymounted in said-cylinder to move between a rst position adjacent thehead end of said air control cylinder and a second position spacedtherefrom, an air control passageway open from the interior of said aircylinder to the interior of said air control cylinder, valve meansoperative to allow passage of air from said air supply passagewaythrough said air cylinder and said air control passageway into said aircontrol cylinder when said oil displacement plunger is at a positionsubstantially entirely within said displacement chamber and operative toblock passage of air through said air control passageway into said aircontrol chamber when said oil displacement plunger is at any otherposition, air control valve means operative in response `to movement ofsaid air control piston to permit passage of air through said air supplypassageway and to block passage of air through said exhaust passagewaywhen air control piston is in said iirst position and to block said airsupply passageway and to permit passageway of air through said exhaustpassageway when said air control piston is in said second position,iirst means operable upon movement of said oil displacement plunger to aposition substantially entirely within said displacement chamber formoving said air piston and said plunger to position said plungersubstantially entirely without said displacement chamber, and secondmeans operable upon movement of said displacement plunger to a positionsubstantially entirely without said displacement chamber for moving saidair control piston from said second to said first position.

3. A hydraulic pump including an oil displacement chamber, a dischargeconduit open from said displacement chamber to a location for use ofhydraulic liuid under pressure, a one way valve for permitting flow ofoil from said displacement chamber through said conduit to said locationfor use, an oil supply tank, an oil intake conduit open from said supplytank to said displacement chamber, a one way valve for permitting flowof oil from said supply tank through said oil intake conduit to saiddisplacementrchamber, `an air cylinder, an air driven piston operablymounted in said cylinder, an oil displacement plunger supported on saidair driven piston toA move therewith from a position substantiallyentirely within Asaid displacement chamber to a position substantiallyentirely without said displacement chamber, an air supply passageway fordelivering air yunder pressure from a source thereof to said aircylinder, an exhaust passageway from inside .said cylinder to outsidethereof, an air control cylinder, an -air control piston operablymounted in said cylinder to move between a iirst position adjacent ahead end of lsaid air control cylinder and a second position spacedtherefrom, an air control ring situated in surrounding relationship tosaid air cylinder, an air control passageway open from the interior ofsaid air cylinder to the interior of said air control ring, said aircontrol pas- .sageway being positioned to beopen to said air cylinder atla side lof said air driven piston adjacent saidk air supply passagewaywhen said oil displacement plunger is at a position substantiallyentirely within said displacement chamber and to vbe sealed off fromsaid air supply passageway by said air driven piston when said oi-ldisplacement plunger is in any other position, an air control pipe openfrom the interior of said air control ring to the interior of said aircontrol cylinder, an air control valve supported on said air controlpiston to move therewith, said air control valve being situated to blockboth said air supply passageway and said exhaust passageway, a rst aircontrol valve port through said air control valve located to have aposition in alinement with said air supply passageway to permit passageof air therethrough when said air control piston is in said firstposition to have a position out of alinement with said air supplypassageway to block said passageway when said air control piston is insaid second position, second air control valve port through said aircon- `trol valve located to have a position in alinement with saidexhaust passageway to permit passage of air through said passageway whensaid air control piston is in its seclond position and to have aposition out of alinement with said exhaust passageway to block saidpassageway when said air control piston is in its first position, meansoperable upon movement of said oil displacement plunger to a positionsubstantially entirely within said displacement chamber for moving saidplunger to a position substantially without said chamber, and meansoperably upon movement of said displacement plunger to a positionsubstantially without said displacement chamber for moving said aircontrol piston from said second to said first position.

4. A hydraulic pump including first and second oil displacementchambers, rst and second discharge conduits each open from thecorrespondingly numbered displacement chambers to a location for use ofhydraulic fluid under pressure, first and second one way valves each forpermitting flow of oil from the corresponding displacement chamberthrough the corresponding discharge conduit to said location for use, anoil supply tank, a single, bifurcated oil intake conduit open fro-m saidoil supply tank to each of said displacement charnbers, valve meansoperative in response to pressure differential between said displacementchambers for alternately permitting flow of oil from said oil supplytank through said oil intake conduit into said first displacementchamber while blocking flow between said second displacement chamber andsaid oil tank through said intake conduit and for permitting flow fromsaid oil supply tank through said oil intake conduit into said secondchamber while blocking flow between said iirst chamber and said oil tankthrough said conduit, first and second air cylinders, first and secondair driven pistons each operably mounted in one of said air cylinders,first and second oil displacement plungers each supported to vmove withthe corresponding air driven piston from a position substantiallyentirely within the corresponding displacement chamber to a positionsubstantially entirely without said displacement chamber, air drivenpiston connecting rods attached to each of said air driven pistons toprovide opposed simultaneous movement of each ofV said pistons withrespect to its corresponding cylinder and of each of displacementplungers with respect 10 to its corresponding displacement chamber,first and second air supply passageways for delivering air underpressure from a source thereof to said first` and second air cylindersrespectively, first and second exhaust passageways each extending frominside of the corresponding air cylinder to the outside thereof, firstand second air control cylinders, rst andVv secondy air control pistonsoperably mounted in said first andsecond air control cylfrom a head endof said secondair control cylinder and' a second position having saidlirst piston spaced from said head end of said first airy controlcylinder and said f second piston adjacent said head end of said secondair control cylinder, first and second air c ontrol passageways eachopen from-the interior of the corresponding air cylinder to the interiorof the corresponding air control cylinder, each of said air controlpassageways beingv positioned to be open to said air cylinder ata sideof its air driven piston adjacent its air supply passageway when itscorresponding oil displacementplunger isin a position substantiallyentirely Within said displacement chamber and to be sealed olf from saidair supply passageway by said air driven piston when said oildisplacement plunger is in any other position, and an air control valveoperative in response to movement of said first and second air controlpistons to allow passage through said first air supply passageway andsaid second exhaust passageway and to block passage through said firstexhaust passageway and said second air supply passageway when said aircontrol pistons are in said first position and to block passage throughsaid first air supply passageway and said second exhaust passageway andto allow passage through said first exhaust passageway and said secondair supply passageway when said air control pistons are in said secondposition. i

5. A hydraulic pump including first and second air cylinders located inconcentric relationship to each other, first and second air drivenpist-ons each operably mounted in a correspondingly numbered one of saidair cylinders, iirst and second oil displacement chambers concentricwith each other and with said air driven pistons, first and second oildisplacement plungers each supported to `move with the corresponding airdriven piston from a position substantially entirely within thecorresponding displacement chamber to a position substantially entirelywithout said displacement chamber, first and second discharge conduitseach open from the correspondingly numbered displacement chamber to alocation for use of hydraulic iiuid under pressure, first and second oneway valves each for permitting flow of oil from. the correspondingdisplacement chamber through the corresponding discharge conduit to saidlocation for use, an oil tank, an oil supply intake conduit open to saidoil supply tank, a displacement chamber communicating passagewayV openbetween said first and second oil displacement chambers and open to saidoil supply intake conduit, an intake valve member slideably supported insaid chamber communieating passageway, and having a first disc Valvesupported thereon in said first displacement chamber and a second discvalve supported thereon in said second displacement chamber, said intakevalve member being moveable to a position to cause said `first discvalve to seal said first displacement chamber irom said intake conduitand to bring said second disc valve into spaced relationship to saidchamber commu ii ating passageway when the pressure in said firstdisplacement chamber is higher than the pres-- sure in said seconddisplacement chamber and movable to and to bring said first disc valveinto spaced relationship 11 to said chamber communicating passagewaywhen the pressure in said second displacement chamber is higher than thepressure in said rst displacement chamber, an air driven pistonconnecting rod fixedly attaching said first and second air drivenpistons to each other, first and second air supply passageways fordelivering air under pressure from a source thereof to said first andsecond air cylinders respectively, first and second exhaust passagewayseach open from inside of the corresponding air cylinder to the outsidethereof, first and second air control cylinders, tirst and second aircontrol pistons opernuly mounted in said first and second air controlcylinders respectively, an air control piston rod connecting said aircontrol pistons to each other, said air control pistons being moveablewith respect to said air control cylinders between a first positionhaving said first air control piston adjacent a head end of said firstair control cylinder and said second air control piston spaced from ahead end of said second air cylinder and a second position having saidtirst piston spaced from said head end of said first air contro-lcylinder and said second piston adjacent said head end of said secondair control cylinder, first and second air control passageways each openfrom the interior of the corresponding air cylinder to the interior ofthe corresponding air control cylinder, each of said air controlpassageways being positioned to be open to the corresponding aircylinder at a side of its air driven piston adjacent its air supplypassageway when its corresponding oil displacement plunger is in aposition substantially entirely within said displacement chamber and tobe sealed off from said air supply passageway by said air driven pistonwhen said oil displacement plunger is in any other position, and an aircontrol valve constituted as portions of said air control piston rodextending through said rst and second air supply passageways and firstand second exhaust passageways, said air control pis ton rod having aplurality of ports therein positioned to allow passage through saidfirst air supply passageway and said second exhaust passageway and toblock passage through said rst exhaust passageway and said second airsupply passageway when said air control pistons are in said instposition and to block passage through said rst air supply passageway andsaid second exhaust passageway and to allow passage through saidl firstexhaust passageway and said second air supply passageway when said aircontrol pistons are in said second position.

References Cited in the le of this patent UNITED STATES PATENTS

